Microphone.



G. ANGELINI.

MICROPHONE.

PPLIoATIoN rILnn 1919.29. 1997.

928,096. Patented July 13, 1909.

Mafmz/Mm UNITED STATES PATENT OFFICE.

GIUSEPPE ANGELINI, OF ROME, ITALY.

MICROPHONE. y

To all whom it may concern.'

Be it known that I, GIUSEPPE ANGELINI, subject of the King ol' Italy, residing at Rome, Italy, have invented certain new and useful Improvements in or Relating to Microphones, of which the following is a speciiication.

This invention relates to a microp'honic transmitter of simple construction which enables the sound to be transmitted in a very powerful way and with great clearness. In order to obtain this result, the parts of the microphone are arranged in such manner that, while maintaining the grains of carbon or the like between the two plates or electrodes oi' the microphone, and. the oscillations oi the plate being sufficiently softened, the latter can produce their maximum eff ect.

The invention is illustrated in the accompanying drawing, in which Figure 1 is a vertical section of the box, the mouthpiece being mounted on the cover -b. Fig. 2 is a front elevation oi the box of the microphone, in the center oi which is placed the adjustable electrode -a.-. Fig. 3 is a cross section of the 'felt ring, and Figs. 4 and 5 are detail views.

In the central portion of the bottom of the box, having the shape of a truncated cone -s-, is mounted a screw fv electrically insulated from the box itself, say by means of an ebonite cylinder -c-. To the upper end of the said screw is soldered or secured the adjustable electrode -aconstituted by a circular disk of carbon or silver plated or gilt metal, rovided with small concentric grooves. A exible mica plate -m-, the diameter oi which is larger than that of the disk -aand on which is placed a layer of wadding -n--, is clamped between the said disk and a metal washer -rscrewed on the screw --u-. By operating the screw -v-, the electrode can be brought nearer to, or moved away from, the disk *Z-w. A lock nut -cserves for securing the screw in the most suitable position.

The carbon disk Zw rests on a felt ring supported on the mica plate -m-, and its edge lies in a recess made in the inner portion. of the box. Between the cover *l2- and the outer edge of the disk is inserted a ring oi' i'elt or other material, which keeps the disk in a fixed position. Screws, not shown in the drawing, serve to secure the cover to the box in a reliable manner.

The felt ring -fhaving a diameter Specification of Letters Patent.

Application led March 28, 1907.

Patented July 13, 1909.

serial No. 365,057.

equal to that of the mica plato and a thickness of only a few millimeters is secured. to the carbon disk, a receptacle thus being formed between the two disks or electrodes, in which the grains of carbon are placed. When the disk is put in place, the felt ring presses against the wadding on the mica plate and thus forms a closed chamber in which the grains are conned between the carbon disk and the adjustable electrode. The mica plate, owing to its elasticity, can follow the vibrations of the carbon disk, and in that way the felt ring does not oppose any resistance to the oscillations of the disk itself, while the adhesion to the felt ring ol the layer of wadding covering the edge of the mica disk, absolutely prevents any grains of carbon from escaping and coming between the mica andthe felt. The grains of carbon being inclosed by the felt ring which forms an integral portion of the disk, are in better condition for immediately assuming all the vibrations of the disk itself. When the electrode au is adjusted in position by turning the screw -fU-, the grains of carbon on the part a will be compressed against the disk -l while the surrounding grains between the outer edge of the disk -a and the felt ring are more or less freely movable. Thus the grains in the center at every vibration of the disk -ZM can receive the greater variations of pressure while the excess will be taken up by the elasticity of the movable mass of grains around the central part, which on account of their mobility will follow the oscillations of the mica disk and continually change their position. In this way a double ellect or combination is obtained, of variation of pressure and variation of position of the grains.

It will be noticed that the recess or cavity in which the grains of carbon are contained, has its walls chiefly formed by soft material like wadding and felt, to which to a certain extent the carbon grains adhere, and which are thus prevented from moving at any slight shock, to which cause is due the humming noise which affects so greatly the clearness of the voice in usual constructions of microphones. The drawbacks of microphones with grains which are too free, are thus avoided, and it may be asserted that the whole of the grains will keep their normal position, while being suliiciently free to participate in the quick vibrations of the disk when a person talks in front of it.

The air tight closing of the cavity contain ing the grains and of the metal box of the microphone, prevents dampness from reaching the grains of carbon.

Electric communications take lace by means of two springs, one of whic presses against the end of the screw -v-, and the other against the groove made in the hub oi' the casing mrs- Having now fully described my said in- Vcntion and the manner in which the same is to be performed, what I claim and desire to secure by Letters Patent ofthe United States of America is 1 1. A microphonic transmitter comprising an outer Vibratory disk, a ring of felt at its under side and in contact therewith, .a fixed electrode constituted by `a rigid plate, a flexi ble disk of greater diameter than the elec- .trode and xed concentrically therein and free and unsupported at its beriphery, a covering of wadding for said exible disk, said Vibratory disk, feit ring, fixed electrode and wadding covered disk forming a closed chamber, and grains of carbon contained in said chamber substantially as and for the purposes set forth.

2. In a microphone transmitter having` a closed grain containing chamber, the cornbination of an outer Vibratory disk, a lower rigid electrode, a flexible disk supporting said electrode, wadding extending around the same and supported upon part of said i'lexible disk, grains of carbon in said chamber and in contact with both said electrode and wadding, the grains of carbon being more closely compacted toward the center than around it, substantially as and for the purposes set forth.

In testimony whereol I have aiiixed my 40 signature in presence of two witnesses.

GIUSEPPE ANGELINI.

Witnesses A. RAZZI, DUILIs NARDONI. 

